How can you increase traffic to a website in the most efficient manner?

I just wanted to know that what is the best approach in SEO or either in paid advertising through an expert can generate or increase the website's traffic. Every people have their own strategy and own perception but I am looking for the best one which will give me the best answer though I can understand what are the areas where I can improve myself while doing digital marketing. Is there any road map through a digital market need to start their career?